Concept:Citizenship involves certain enforceable duties, and paying tax is one such fundamental obligation to the state.
Explanation:A citizen is expected to perform compulsory duties towards the state.
Examples include paying taxes, defending the country when called upon, and giving evidence in court when required.
Tax payment is essential because the government needs revenue to carry out developmental projects.
Supporting the government in power is a matter of personal choice, not a legal duty.
Reciting the national pledge is a symbolic act and not an enforceable obligation.
Encouraging other citizens is commendable but does not rank as an essential duty.
Thus, among the given options, the essential duty of a citizen to the state is the payment of tax.
Answer:C. pay his tax